IL4 and parasitic infectious disease: Toll receptor stimulation of mast cells and basophils, principally via TLR2 activation by proteases such as Der p 1 and hookworm antigens, forms the predominant source of IL‐4 in allergen and helminth parasite‐activated PBMCs, suggesting an evolutionary role for basophils and mast cells in antigen presentation in MHC class II molecules and for induction of IL‐4 production and Th2 responses in the immunity to parasite infection 30, 31.